Nitrogen Cycle in Water
author: Louise Odale
advisor: Lawrence Griffin
INTRODUCTION: In 1665, the first hint of sub-visible organisms living in water, was made when Antony Leeuenhock turned his microscope on a drop of water and discovered it to be teeming with "minute animalcules". Although it was not until about two centuries later, 1840, that Louis Pasteur began pronouncing different ones of these "animalcules" as dangerous, Leeuenhock's discovery seems to me to have been the beginning of water examination. Today, the study of these small water organisms, bacteria, constitutes one of the most important branches of water analysis. With the aid of modern methods, it is now possible to determine whether the bacteria present form a source of disease; or whether they are harmless, natural inhabitants of the water.
To discover the kind and number of these microorganisms in any water, it is necessary to conduct a bacteriological examination. A chemical analysis of the water must also be made to find the organic and inorganic materials that may be present which would form a source of food supply for bacteria. This latter examination thus gives the necessary information to explain the presence of the bacteria found, since each of the bacterial forms require specific kinds of food. The chemical examination also provides, if pollution existed at some past time or is now present the information regarding the progressive changes the water has undergone from the time it passed through the polluted source to the time it would be fit for consumption. This determination involves, particularly, one branch of water purification: the stages undergone in the putrefaction or fermentation of protein materials and their subsequent nitrification to harmless nitrogenous salts.
To study this process, I used the water in the small lake back of Reed College. The laboratory methods involved in the analysis I was able to make, are those of the manual on "Standard Methods of Water Analsis," published in 1925 by the American Public Health Association; and the "Laboratory Guide in General Bacteriology", published in 1927 by Harold J. Conn. The research material is taken from a number of different sources (a bibliography may be found at the end of the thesis) and is intended to gather together and organize the data pertaining to the relationships of nitrogenous material from a chemical and bacteriological standpoint.